The development and popularity of microwave ovens has required and encouraged the coincidental development of containers and accessories adaptable for use within the microwave ovens because of the unique qualities of the microwave system.
The microwave oven has greatly changed the food preparation habits of both the family and commercial food establishments. The microwave oven is fast, efficient, and clean. The food preparer may cook food in serving dishes, or even, at times, on the plates from which the food is to be eaten. Especially, food may be warmed on dinner plates. Thus, cooking pots, pans, and trays are frequently eliminated, saving additional preparation and cleaning time and work beyond the time and effort saved by the use of the microwave oven itself.
As is well-known, and emphasized in the prior art, many materials are considered transparent to microwaves, such as paper, glass, ceramics, and various plastics. These microwave transparent materials are in common use as food containers adaptable for heating in microwave ovens, either as original containers for such food items as frozen foods, as utensils for fast and efficient cooking of food, or as containers useful in warming over cooked foods.
Whenever food is heated in a microwave oven, the container should be covered with a microwave transparent material to prevent spattering of food particles throughout the interior of the oven. Spattering normally occurs as water molecules within a restricted portion of food are rapidly converted to steam by the microwave energy. In contrast, when an uncovered cup of water is being heated in the microwave oven, the water will be able to absorb the microwave energy gradually and evenly and become heated to the boiling point without spattering. Thus, where water is tightly enclosed within a small food particle, or essentially encapsulated, as, for example, within a kernel of popcorn, the conversion to steam is sudden and violent, and the energy derived from the sudden expansion will carry food particles away from the container. Other normal organic fluids within the food will react similarly.
We have become increasingly knowledgeable of the capabilities, benefits, uses, and limitations of microwave ovens, we have designed and developed convenient equipment, packaging components and methods, and heating containers to accommodate further specific purposes as our knowledge increases. The prior art discloses many examples of packages and containers which have been developed for use with microwave ovens. In my own search efforts, I have noted the following patents for packages and containers which were designed for microwave ovens or adapt able for such use:
______________________________________ 2,687,026 Gleason Aug. 24, 1954 4,345,133 Cherney et al Aug. 17, 1982 4,425,368 Watkins Jan. 10, 1984 4,532,397 McClelland July 30, 1985 4,563,561 Vaeth et al Jan. 7, 1986 4,574,174 McGonigle March 4, 1986 ______________________________________